This invention relates in general to networks of electronic controllers for controlling the operation of a plurality of output devices. In particular, this invention relates to improved structure for a network of electronic controllers in which each of the controllers is responsive to the environment in which it is located for automatically adopting a selected one of a plurality of operating programs stored therein for execution.
Electronic controllers are often used for controlling the operation of one or more output devices in response to one or more input conditions. A typical electronic controller contains an operating program that periodically samples electrical input signals that are representative of the various input conditions. When one or more predetermined input conditions have been satisfied, the electronic controller generates electrical output signals that control the operation of one or more of the output devices. When it is necessary to monitor a relatively large number of input conditions or to control a relatively large number of output devices, it is known to embody the electrical controller as two or more microprocessors (electronic controllers of relatively small computational or control capabilities) that are connected together in a network. The use of a plurality of relatively small microprocessors in lieu of a single relatively large electrical controller has been found to be advantageous for cost and other considerations.
For example, it is known to provide commercial and industrial vehicles with a plurality of hydraulic actuators that are adapted to perform a variety of specific tasks in response to various input signals. By way of illustration, a conventional garbage truck is usually provided with a plurality of hydraulically powered output devices, such as an arm adapted to reach out, grip, lift, and dump a garbage container into a storage hopper carried thereon. A variety of hydraulic actuators are necessary to perform these functions. In the past, the hydraulic actuators were manually operated by a driver of the vehicle. More recently, however, the operation of the hydraulic actuators is controlled by a network of microprocessors carried on the vehicle. Each of the microprocessors contains an individual operating program that is designed to monitor certain input conditions and, in response thereto, operate certain hydraulic actuators on the vehicle. A separate microprocessor may be provided for facilitating input and output communication with the driver of the vehicle. The network of microprocessors functions as a unit to control the operation of the various hydraulic actuators in a desired manner.
From time to time, individual microprocessors within such a network may fail and require replacement. Ideally, such replacement should be performed as quickly as possible to minimize the downtime of the vehicle. The process of physically replacing the microprocessor can be performed in a relatively quick and simple manner. However, it has been found that the further process of re-programming the new microprocessor to perform the specific tasks previously assigned to the failed microprocessor can be relatively time consuming and require the use of trained service personnel. The difficulty of this re-programming is further exacerbated when the microprocessors are carried on a vehicle that is located a great distance from trained service personnel. Thus, it would be desirable to provide an improved structure for a network of microprocessors that avoids this problem.